熔纺氨纶交联剂控制系统的改进

用双泵代替单泵来控制交联剂的添加。交联剂经一级泵,采用压力闭环控制系统,产生较高的稳定的压力,再经二级泵,采用速度开环控制,达到准确的流量,解决了单泵系统难以同时控制2个被控量的难题,满足了熔纺氨纶工艺的要求。     

Binding of the globular domain of linker histones H5/H1 to the nucleosome: a hypothesis

The amino acid sequence of the central globular domain of histoneH1/H5 family members is highly homologous. Twenty-four suchsequences have been compared to establish the conserved andvariable residues. Fitting this to the tertiary structure ofthe H5 globular domain shows which of the conserved and variableresidues are peripheral and which internal. Particular attentionis paid to conserved basic residues on the surface, which wetake to be DNA binding. Variable regions and conserved acidicresidues are assumed not to be sites of contact with DNA. Weconclude that one face of the domain, containing a cluster ofbasic residues, is the principal DNA binding site whilst twoopposing faces, orthogonal to the principal site and also containingconserved basic residues, are subsidiary DNA binding sites.Since the DNA binding surface of the domain covers a full 180°arc, we propose that it contacts a ‘cage’ of threeDNA strands on the 2-fold axis of the chromatosome.     

Properties of a single-chain antibody containing different linker peptides

Single-chain antibodies were constructed using six differentlinker peptides to join the V_H and V_L domains of an anti-2-phenyloxazolone(Ox) antibody. Four of the linker peptides originated from theinterdomain linker region of the fungal cellulase CBHI and consistedof 28, 11, six and two amino acid residues. The two other linkerpeptides used were the (GGGGS)₃ linker with 15 amino acid residuesand a modified IgG2b hinge peptide with 22 residues. Proteolyticstability and Ox binding properties of the six different scFvderivatives produced in Escherichia coli were investigated andcompared with those of the corresponding Fv fragment containingno joining peptide between the V domains. The hapten bindingproperties of different antibody fragments were studied by ELISAand BIAcore^TM. The interdomain linker peptide improved the haptenbinding properties of the antibody fragment when compared withFv fragment, but slightly increased its susceptibility to proteases.Single-chain antibodies with short CBHI linkers of 11, six andtwo residues had a tendency to form multimers which led to ahigher apparent affinity. The fragments with linkers longerthan 11 residues remained monomeric.     

Effect of peptide linker length and composition on immobilization and catalysis of leucine zipper‐enzyme fusion proteins

Linkers are critical components of fusion proteins, as they physically separate individual domains to enable each to fold and retain function. The role of peptide linker properties was investigated for fusions of a leucine zipper immobilization domain (Z_E) to a chimeric amine dehydrogenase (AmDH) or a formate dehydrogenase (cbFDH). A linker library was developed, which varied in length, orientation, and proline content, as a way to vary stiffness. Fusion proteins were characterized by melting temperature, immobilization ability, cofactor binding, and kinetic activity. The best linker candidate for each enzyme was tested in a dual‐functionality assay, where enzymatic activity of fusions immobilized in protein‐inorganic supraparticles was greater than 80% after washing. The best linker for AmDH was completely different than that for cbFDH. This work highlights the need to experimentally assess linker properties in the design of new fusion proteins and provides a linker library for this purpose. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2934–2946, 2018     

An improved linker for single-chain Fv with reduced aggregation and enhanced proteolytic stability

The effects of linker length on binding affinity and degreeof aggregation have been examined in the antifluorescein 4-4-20and anticarcinoma CC49 single-chain Fvs. Longer linkers in theantifluorescein sFvs have higher affinities for fluoresceinand aggregate less. A proteolytically susceptible site betweenLys8 and Ser9, in the previously reported 212 linker has beenidentified. A new linker sequence, 218 (GSTSGSGKPGSGEGSTKG)was designed in which a praline was placed at the C-terminalside of the proteolytic clip site in the 212 linker. The CC49sFv containing the 218 linker showed reduced aggregation andwas found to be more stable to proteolysis in vitro, when comparedto the CC49/212 sFv. The CC49 sFv with the longer 218 linkerhad higher affinity than CC49/212 sFv. An aggregated CC49/212sFv sample had higher affinity than CC49/218 sFv. The CC49/218and CC49/212 sFvs had similar blood clearances in mice, whilethe aggregated CC49/212 sFv remained in circulation significantlylonger. In mice bearing LS-174T human colon carcinoma xenografts,the CC49/218 sFv showed higher tumor uptake than the CC49/212sFv and lower tumor uptake than the aggregated CC49/212 sFv.The higher tumor uptake of the CC49/218 is most likely a resultof its higher resistance to proteolysis. The higher affinityand higher tumor uptake of the aggregated CC49/212 sFv are mostlikely due to the repetitive nature of the TAG-72 antigen andthe higher avidity of multivalent aggregates. When the sFvswere radiolabeled with a lutetium-chelate the CC49/218 sFv showeda lower accumulation in the liver and spleen compared to theaggregated CC49/212 sFv.     

An active single-chain antibody containing a cellulase linker domain is secreted by Escherichia coli

Single-chain antibodies consist of the variable, antigen-bindingdomains of antibodies joined to a continuous polypeptide bygenetically engineered peptide linkers. We have used the flexibleinterdomain linker region of a fungal cellulase to link togetherthe variable domains of an anti-2-phenyloxazolone IgGl and showhere that the resulting single-chain antibody is efficientlysecreted and released to the culture medium of Escherichia coli.The yield of affinity-purified single-chain antibody is 1 -2mg/1 of culture medium and its affinity and stability are comparableto those of the corresponding native IgG.     

A novel approach to scheduling multipurpose batch plants using unit‐slots

Several models for scheduling multipurpose batch plants exist in the literature. The models using unit‐specific event points have shown better solution efficiency on various literature examples. This article presents a novel approach to scheduling multipurpose batch plants, which uses unit‐slots instead of process‐slots to manage shared resources such as material storage. We develop two slightly different models that are even more compact and simpler than that of Sundaramoorthy and Karimi, Chem Eng Sci. 2005;60:2679–2702. Although we focus on material as a shared resource, our multi‐grid approach rationalizes, generalizes, and improves the current multi‐grid approaches for scheduling with shared resources. Our models allow nonsimultaneous transfers of materials into and out of a batch. We show by an example that this flexibility can give better schedules than those from existing models in some cases. Furthermore, our approach uses fewer slots (event‐points) on some examples than even those required by the most recent unit‐specific event‐based model. Numerical evaluation using literature examples shows significant gains in solution efficiency from the use of unit‐slots except where the number of unit‐slots required for the optimal solution equals that of process slots. We also highlight the importance of constraint sequencing in GAMS implementation for evaluating mixed‐integer linear programming based scheduling models fairly. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Photo-DSC I: A new tool to study the semi-crystalline polymer accelerated photo-ageing

Photo-DSC was used, to study, in situ, the photo-ageing of polycyclo-octene which is a semi-crystalline elastomer. The ‘crystallizability’, which is the ability of the polymer to crystallize, was tightly dependent on the exposure time and was used to follow the photo-ageing.The irradiation system of photo-DSC was also compared with a usual accelerating device and no difference was detected in the chemical alteration of the polymeric matrix. Meanwhile, with photo-DSC, the photo-ageing was accelerated compared to a usual accelerating device. By using photo-DSC, atmosphere, exposure time, light intensity and ageing temperature were accurately controlled.     

一种新型脂肽的分离纯化及其生物学活性

目的从表皮葡萄球菌发酵液中分离纯化脂肽粗提物,并分析其生物学活性。方法通过酸沉淀分离和有机溶剂抽提的方法,从表皮葡萄球菌1457发酵液中得到脂肽粗提物。利用排油圈试验和薄层色谱(TLC)分析脂肽粗提物的性质,HPLC分析其纯度。小鼠皮下注射脂肽粗提物后,再经皮肤感染金黄葡萄球菌,检测其对小鼠体内白细胞的影响及抑菌作用;实时定量PCR检测其对小鼠体内β防御素14(mBD14)表达的影响。结果所得脂肽粗提物F2的排油活性大于F1;TLC分析显示,F2中存在性质相近的脂肽类同系物,纯度>60%;脂肽粗提物能减缓小鼠因感染金黄葡萄球菌引起的急性炎症,降低由感染引起的白细胞增多,并通过上调mBD14的表达抑制细菌在皮肤内的增殖。结论已从表皮葡萄球菌发酵液中成功获得了具有生物学活性的新型脂肽粗提物。     

A wavelet‐Fisz approach to spectrum estimation

Abstract. We propose a new approach to wavelet threshold estimation of spectral densities of stationary time series. Our proposal addresses the problem of heteroscedasticity and non‐normality of the (tapered) periodogram. We estimate thresholds for the empirical wavelet coefficients of the periodogram as appropriate linear combinations of the periodogram values similar to empirical scaling coefficients. Our solution introduces ‘asymptotically noise‐free reconstruction thresholds’ which parallels classical wavelet theory for nonparametric regression with independently and identically distributed Gaussian errors. Our simulations show promising results that clearly improve on existing approaches. In addition, we derive theoretical results on the near‐optimal rate of convergence of the minimax mean‐square risk for a class of spectral densities, including those of low regularity.     

Synthesis,characterization, and tunable adsorption and diffusion properties of hybrid ZIF‐7‐90 frameworks

Hybrid zeolitic imidazolate frameworks (ZIFs), containing more than one type of imidazolate linker, can allow highly tunable molecular sieving and adsorption. Their crystallization becomes more challenging when the end‐member (single‐linker) ZIFs crystallize in different crystal systems. We demonstrate the controlled synthesis and detailed characterization of hybrid ZIF‐7‐90 frameworks containing linkers of ZIF‐7 (rhombohedral) and ZIF‐90 (cubic). ZIF‐7‐90 materials with SOD‐type topology are obtained in three crystalline phases depending on the linker composition and synthesis technique. The effect of synthesis conditions on the activation‐induced phase transition from rhombohedral to other topologies is studied. Nitrogen physisorption at 77 K and CO₂ physisorption at 273 K shows the tunability of the pore‐size distribution and the framework flexibility as a function of framework composition. Measurements of water adsorption and butane isomer diffusion illustrate the tunability of diffusivity over seven orders of magnitude and control of hydrophobic to hydrophilic adsorption behavior. © 2015 American Institute of Chemical Engineers AIChE J, 62: 525–537, 2016     

Modeling pressure drop coefficient for cyclone separators: A support vector machine approach

As one of performance critics for cyclone separators, pressure drop is an important parameter to evaluate and design cyclone separators. In order to accurately predict the complexly nonlinear relationships between pressure drop coefficient (PDC) and geometrical dimensions, a support vector machine (SVM) model is developed and employed to model PDC for cyclone separators. Based on the normalization method and the random sampling technique for the experimental sample dataset, a dynamically optimized search technique with cross validation is introduced to determine optimal algorithm parameters in the model. Then the optimized SVM model is trained and tested by the simulation results. According to the predicted accuracy of PDC for cyclone separators, the SVM model performance is compared and evaluated. It is found that the SVM model provides the higher generalization performance than the conventional models including the theoretical and statistical models as well as the artificial neural network model, with the mean squared error of 3.64×10⁻⁴ and the correlation coefficient of 0.9974. The result also demonstrates that SVM can offer an alternative and powerful approach to model cyclone pressure drop.     

Functionalization of gauzes with liposomes entrapping an anti-inflammatory drug: A strategy to improve wound healing

From ancientness, suitable materials have been developed to cover the wounds in order to prevent infections and promote proper wound healing. In this study, the successful development of functionalized nonwoven gauzes with liposomes entrapping anti-inflammatory piroxicam is reported. Piroxicam is a non-steroidal anti-inflammatory drug (NSAID) that can suppress a persistent inflammatory response, leading to improved wound healing. The results demonstrated that the highest NSAID concentration released is achieved when gauzes were previously cationized with poly(diallyldimethylammonium chloride) (PDDA) and high concentration of phospholipid (≈3000 μM) and multilamellar liposomes (MLVs) were used. MLVs were also the best vehicle considering their biocompatibility with skin human fibroblasts, where no toxicity was observed for neither of the tested conditions.The developed functionalized gauzes can be, therefore, a good strategy to treat chronic wounds.     

Design and Synthesis of Cross-Linked Micellar Particles to Assist Microalgae Lipid Recovery from Aqueous Extract

A series of cross‐linked micellar particles (CLMP) with internal hydrophobic binding sites was synthesized via a double‐cross‐link concept. A quaternary ammonium surfactant was first synthesized from natural tung oil. With two acrylate groups in the head group and conjugated alkenes in the hydrophobic tail, the surfactant was doubly cross‐linked in the micellar form on both the micellar surface and in the core. Surface cross‐linking at ambient temperature and core cross‐linking at 80 °C yielded 61 % final product (with 40 % space holder). The product and its morphology were characterized by infrared (IR) spectroscopy and scanning electron microscopy (SEM). The chemical nature and functional groups were confirmed by IR, and SEM indicated heterogeneous nanoparticles aggregated into clusters of particles. The binding capacity and selectivity of CLMP for microalgae lipids extracted from Nannochloropsis sp. were investigated and quantified using a turbidity test and mass spectrometry. The best CLMP product was able to extract total algae lipids at 0.8 g lipids/g particles capacity. At a lipid loading above the binding capacity, the CLMP selectively bound non‐charged polar lipids instead of the negatively charged polar lipids. These micellar particles have been demonstrated to be promising materials for extracting lipids from aqueous lipid extract. This paper presents a proof of concept study, and more in‐depth investigation is needed to test lipid extraction from various media and potentials for lipid class separation using these structured particles.     

Design of a Rubbery Carboxymethyl Cellulose/Polyacrylic Acid Hydrogel via Visible‐Light‐Triggered Polymerization

Hydrogels, as soft and wet materials, have attracted great attention in the field of functional biomaterials. Most recently, the designed hydrogels, according to the energy dissipation principle, overcome the low mechanical strength, poor toughness, and limited recoverability of common hydrogels and show excellent mechanical properties. However, most of these novel designed hydrogels are lacking of instantaneous recovery and antifatigue properties. In this study, a mesoscopic inhomogeneous hydrogel consisting of carboxymethyl cellulose and polyacrylic acid is synthesized through a facile, one‐pot, visible‐light‐triggered polymerization. The prepared hydrogel can be stretched over 700% with fracture strength as high as 850 kPa, and shows a high elastic modulus (180 kPa). The microgel aggregated structure endows an efficient energy dissipation mechanism to the hydrogel. After the internal network structure stabilizing, the hydrogel exhibits a recovery time within 10 ms and over 92% resilience during impact and cyclic tensile tests, respectively. The hydrogel with such excellent mechanical properties can extend its application in biomaterial fields.

     

Fabrication of Cross‐Linked Anion Exchange Membranes Using a Pillar[5]arene Bearing Multiple Alkyl Bromide Head Groups as Cross‐Linker

A pillararene‐based macrocycle with up to 10 flexible chains bearing alkyl bromide head groups is synthesized and investigated for the first time as a multiarm cross‐linker for tertiary‐amine functionalized polyethersulfone. Different from any previously reported cross‐linker, this has a unique pillar‐shaped structure and abundant reactive sites to form multifunctional clusters in the conductive domain. This advantage enables cross‐linking to occur smoothly at the membrane‐casting stage and endows the cross‐linked membranes with improved performance. The cross‐linked anion exchange membranes are found to possess high conductivities and excellent alkaline stability. With a controllable swelling ratio of 19.5%, the maximum conductivity of a membrane can reach 155 mS cm^–1 at 80 °C. Due to its local high‐density cross‐linked structure, a delay in degradation kinetics under alkaline condition can be observed, and the loss of conductivity is <10% after 400 h of alkaline stability test at 80 °C.     

Divinyl benzene cross‐linked HTPB‐based polyurethaneurea membranes for separation of p‐/o‐xylene mixtures by pervaporation

Cross‐linked hydroxy terminated polybutadiene (HTPB)‐based polyurethaneurea (PU), HTPB‐divinyl benzene (DVB)‐PU, was synthesized by a three‐step polymerization process. It was first used as membrane material to separate p‐/o‐xylene mixtures by pervaporation (PV). The effects of the content of cross‐linker DVB, feed concentration, and operating temperature on the PV performance of HTPB‐DVB‐PU membranes were investigated. The membranes demonstrated p‐xylene permselectivity as well as high total flux. The introduction of DVB significantly enhanced the temperature resistance ability of the HTPB‐DVB‐PU membranes. With increasing DVB content, the separation factor increased while the total flux decreased a little. The highest separation factor reaches 2.01 and the total flux is 33 g/m²h with feed concentration of 10 wt % p‐xylene at 30°C. These PV performances with increasing DVB content were explained in terms of the view point of chemical compositions and physical structures of the HTPB‐DVB‐PU membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012